# Boosting superconductivity in ultrathin YBa2Cu3O7−δ films via nanofaceted substrates

## TL;DR

This paper shows that using nanofaceted substrates can boost superconductivity in ultrathin YBa2Cu3O7−δ films by enhancing the onset temperature and magnetic field.

## Contribution

The novel approach of using nanofaceted substrates to enhance superconductivity through electronic nematicity and charge density waves is introduced.

## Key findings

- Nanofaceted substrates significantly increase the superconducting onset temperature and upper critical magnetic field in ultrathin films.
- Electronic nematicity and unidirectional charge density waves are identified as key drivers of the observed enhancement.
- The unique interface between the film and nanofaceted substrate introduces an effective potential that promotes superconductivity.

## Abstract

In cuprate high-temperature superconductors the doping level is fixed during synthesis, hence the charge carrier density per CuO2 plane cannot be easily tuned by conventional gating, unlike in 2D materials. Strain engineering has recently emerged as a powerful tuning knob for manipulating the properties of cuprates, in particular charge and spin orders, and their delicate interplay with superconductivity. In thin films, additional tunability can be introduced by the substrate surface morphology, particularly nanofacets formed by substrate surface reconstruction. Here we show a remarkable enhancement of the superconducting onset temperature \documentclass[12pt]{minimal}
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\begin{document}$${T}_{{{{\rm{c}}}}}^{{{{\rm{on}}}}}$$\end{document}Tcon and the upper critical magnetic field Hc,2 in nanometer-thin YBa2Cu3O7−δ films grown on a substrate with a nanofaceted surface. We theoretically show that the enhancement is driven by electronic nematicity and unidirectional charge density waves, where both elements are captured by an additional effective potential at the interface between the film and the uniquely textured substrate. Our findings show a new paradigm in which substrate engineering can effectively enhance the superconducting properties of cuprates. This approach opens an exciting frontier in the design and optimization of high-performance superconducting materials.

The authors report an enhancement of the superconducting onset temperature in nanometer-thin YBa2Cu3O7-δ films grown on substrates with nanofaceted surfaces. They theoretically show that the enhancement is mainly driven by electronic nematicity and unidirectional charge density waves, and further suggest that the nanofacets themselves may promote these effects.